ceilings and lighting effects

Hello everyone, I am a new subscriber to this site and I wish to solicit some of your ideas about designs for ceilings and lighting effects on my newly built two storey house of about a 100 square meter floor area.

If you are inside the second floor, you will be able to see the exposed steel purlins, trusses and roof insulator. I want to turn the looks into something creative and beautiful. It is a high roof of about 20 feet at the apex. Thus, when you go inside the second floor it has the effects of a big space. And I want to preserve that "big space" effect. That is why i just would not want to put up a ceiling to prejudice my concept. What i wanted to find out is what other designs of ceiling and lighting effects can i do to make a bare looking top beautiful, with the "big space" effect?